CN102145946B

CN102145946B - Method for treating trace amount of cadmium in wastewater by chelation, coagulation and ultrafiltration combination

Info

Publication number: CN102145946B
Application number: CN 201110041487
Authority: CN
Inventors: 赵旭; 刘会娟; 陈发源; 彭丽霞; 兰华春
Original assignee: Research Center for Eco Environmental Sciences of CAS
Current assignee: Research Center for Eco Environmental Sciences of CAS
Priority date: 2011-02-21
Filing date: 2011-02-21
Publication date: 2013-06-26
Anticipated expiration: 2031-02-21
Also published as: CN102145946A

Abstract

The invention belongs to the technical field of water treatment, and in particular relates to a method for removing cadmium in high salt wastewater of a metallurgy industry by chelation and coagulation combination. The cadmium in various forms in the high salt wastewater is difficultly removed effectively by the conventional single method, so that a combination method for removing a trace amount of cadmium in water by chelation and coagulation of inorganic polymer and ultrafiltration. The method comprises the following steps of: chelating the cadmium in various forms by using ethylene diamine tetraacetic acid disodium salt (EDTA disodium salt); coagulating chelates of the cadmium and the EDTA disodium salt by using polyaluminium chloride (PAC); and performing effective filtration treatment by using an ultrafiltration unit to effectively remove the trace amount of cadmium in the water. The method is mainly applied to advanced wastewater treatment in the metallurgy industry and can also be applied to the effective removal of high salt heavy metal from wastewater in other industries.

Description

The method of Trace Cadmium in a kind of chelating-coagulation-ultrafiltration combined treatment waste water

Technical field

The invention belongs to technical field of waste water processing, the method that particularly in high-salt wastewater, Trace Cadmium is removed.

Background technology

The discharging of trade effluent is the major cause of heavy metal in water cadmium pollution, and the heavy metal contamination that wherein mining, ore dressing, metallurgy industry cause is especially serious.Cadmium (Cd) toxicity is very large, can accumulate in human body, mainly is accumulated in kidney, can cause serious harm to kidney, causes the variation of urinary system; Destroy the metabolism of calcium in body, namely replace the calcium in bone and make bone become soft, disuse atrophy occurs at last; Immunologic function there is restraining effect, can reduces the homeostatic function of body, finally lead oncogenic generation.So in " water environment quality standard " (GB 3838-2002), the emission limit of cadmium is minimum, requires the tightest.

Have suspended substance and colloid except mixing in non-ferrous metals industry waste water, and contain a large amount of harmful metal ions, as: Cd, Pb, As, Cr, Hg, Cu, Zn etc., and nonmetallic ion component, as Na ⁺, K ⁺, Ca ²⁺, Mg ²⁺, SO ₄ ^2-, Cl ^-, F ^-, CN ^-, S ^2-, NO ₃ ^-Deng.Chemical precipitation method and coagulation and filtration method can make most of heavy metal be removed, and concentration of heavy metal ion but also has with a certain distance from qualified discharge below 0.1mg/L.

The removal method of cadmium ion comprises chemical precipitation method and materialization partition method two classes.Can adopt basic agent to form the precipitation of hydroxide of cadmium, or add the sulfide precipitation that hydrogen sulfide, sodium sulphite or Iron sulfuret form cadmium.Cadmium ion is easy and NH at the aqueous solution ₄ ⁺, CN ^-, Cl ^-Deng generating complexing ion.Especially with chlorion, usually electroplate and metallurgy industry in contain the chlorion of high density, chlorion and cadmium ion easily form complex compound and are difficult to by the method that precipitates and adsorb its effective removal.The materialization partition method can adopt the technology such as ion-exchange, reverse osmosis, evaporation cadmium is separated and reclaim.The ion-exchange cost is high, resin needs regeneration and unstable for Trace Cadmium removal capacity in high-salt wastewater; The evaporation cost is high, generally through engineering approaches is not used; Reverse osmosis investment and running cost are high, and producing water ratio is low, and concentrated solution is many and difficult, easily cause salt accumulation simultaneously.

Therefore, as how existing chemical precipitation and coagulation and filtration technique are the basis, do not carrying out or be difficult in time carry out under the condition of extensive technological transformation, solve in high-salt wastewater a Trace Cadmium qualified discharge difficult problem or successfully manage the water quality security that sudden cadmium pollution event causes, having important practical significance.

The present invention proposes around two critical process such as chelating and coagulations a kind of method that in metallurgical high-salt wastewater, Trace Cadmium is effectively removed.The present invention is mainly used in micro-hydrolysate in metallurgical high-salt wastewater, also can be applicable to micro-hydrolysate or waste water recycling etc. in the electroplating industry high-salt wastewater.

Summary of the invention

The present invention seeks to the problem that is difficult to remove for Trace Cadmium in high salt industrial waste water, a kind of economy, effectively and the method that is easy to use in engineering is provided, realize discharged wastewater met the national standard with effective removal Trace Cadmium, or further advanced treatment reaches the process water reuse standard.

Know-why of the present invention is, cadmium easily forms medium stable comple with many organic compound that contain soft ligating atom (S, Se, N), especially can with contain-the strong chelating of amino acids ligand of SH base, cadmium is extracted from the complex state of itself and Cl.Disodium EDTA (EDETATE DISODIUM) is polydentate ligand, coordinate with cadmium ion to generate to have a plurality of pentacyclic inner complexs, and the stability constant of formed inner complex is all very large.Because it has 6 ligating atoms, can satisfy the ligancy of most metal ions, in the ordinary course of things, the proportioning of these inner complexs is all 1: 1.Polymerize aluminum chloride (PAC) is widely used in water treatment, is a kind of inorganic polymer water treatment agent, is mainly due to OH ^-Bridging action and the polymerization of multivalent anions and produce the complex compound that molecular weight is large, electric charge is higher.By the cadmium chelating of ethylenediamine tetraacetic acid (EDTA) (EDTA) sodium salt with different shape, next, get off by PAC throwing out inner complex coagulation, thereby make cadmium be able to effective removal.

The technical scheme that the present invention takes is as follows:

1.EDTA dissolve respectively with PAC and be mixed with required certain density liquid.Described EDTA is the technical grade chemical reagent, and described PAC is characterized in that the technical grade solid sample.

2. certain density EDTA solution is added to the Trace Cadmium waste water of pending high saliferous, dosage calculates with the throwing amount of EDTA, and the concentration of EDTA is between 10～100mg/L.

3.EDTA after solution adds to the pending water, carry out the mechanical stirring reaction, churning time was controlled at less than 0.5 hour.With cadmium from complex state that Cl forms extract and form more stable complex compound with EDTA or cadmium forms complex compound with EDTA together with Cl.

4. water outlet enters coagulating sedimentation, pond, adds PAC with the inner complex flocculation of cadmium and EDTA formation, and the PAC dosage is 10～50mg/L.

5. through the water sample process uf processing of chelating precipitation process, the Trace Cadmium in water can effectively be removed.

Technical characterstic of the present invention is as follows:

1. need not to carry out the large-scale engineering transformation and can effectively remove Trace Cadmium, be easy to realize in engineering;

2. use operating process easy, need not to increase complicated operation bidirectional on water treatment plant or treatment station daily operation management basis;

3. adopt medicament to be water purification medicament or water-purifying material commonly used in water treatment, with low cost;

4. other micro heavy ion remavals in water also there is good promoter action.

Description of drawings

Accompanying drawing is the process flow sheet that the inventive method is removed Trace Cadmium.

Embodiment

Embodiment 1

In smeltery, Yunnan Metallurgical Waste Water treatment process, the nanofiltration water outlet is research object, and in the carbon filtrate, the concentration of cadmium ion is 0.019～0.025mg/L, Cl ^-Concentration is the 2500mg/L left and right, and initial pH is 11.

Adopt method of the present invention to remove cadmium: 1) to get certain volume nanofiltration water outlet, add the EDTA of 10mg/L, stirred the cadmium chelating of various different shapes 25 minutes.2) add respectively again the PAC coagulation 30 minutes of 50mg/L, with chelating the EDTA flocculating settling of cadmium get off.3) carry out uf processing through ultra-filtration membrane.It is 0.0048mg/L that analysis records residual cadmium amount, reach II class Cadmium In The Water Body in " water environment quality standard " (GB 3838-2002) limit value (≤0.005mg/L).

Embodiment 2

In certain smeltery's Metallurgical Waste Water treatment process, the carbon filter water outlet is research object, and in the carbon filtrate, the concentration of cadmium ion is 0.045～0.054mg/L, Cl ^-Concentration is the 2500mg/L left and right, and initial pH is 10.84.

Adopt method of the present invention to remove cadmium: 1) to add the EDTA of 10mg/L in the carbon filter water outlet, stir chelation treatment 0.5h.2) add the PAC coagulation 0.5h of 100mg/L, with chelating the EDTA flocculating settling of cadmium get off.3) ultra filtration unit is carried out uf processing.4) analyze that to record residual cadmium amount be 0.0041mg/L, reach II class Cadmium In The Water Body in " water environment quality standard " (GB 3838-2002) limit value (≤0.005mg/L).

Claims

1. the method for the Trace Cadmium in high-salt wastewater is removed in an EDETATE SODIUM salt chelating and inorganic polymer flocculation combination, it is characterized in that the concentration of Trace Cadmium in waste water is between 0.019 to 0.025mg/L, first the cadmium with different shape in EDETATE SODIUM salt pair high-salt wastewater carries out chelating, then with polymerize aluminum chloride PAC flocculation agent flocculation coagulation, next process by ultra filtration unit, in water outlet, Trace Cadmium is effectively removed.

2. in accordance with the method for claim 1, the dosage scope of EDETATE SODIUM salt is 10-100mg/L, and the chelatropic reaction time was less than 0.5 hour.

3. in accordance with the method for claim 1, PAC dosage scope is 10-50mg/L, and flocculation precipitation reaction was less than 0.5 hour.

4. in accordance with the method for claim 1, it is characterized in that the flocculation sediment water outlet enters ultra filtration unit, carries out uf processing.